Method for producing superconductive wires of multifilaments which are encased in copper or a copper alloy and contain niobium and aluminum

Claim 1

A method for producing a superconductive wire of multifilaments having components comprising niobium and aluminum encased in copper or a copper alloy, wherein the multifilament configuration and the formation of a superconductive Al5 phase are positively developed from the components disposed in a copper or copper alloy tube having an interior metallic coating serving as a diffusion barrier, by cold forming and subsequent heat treatment, comprising the steps of: (a) mixing to form a powder mixture, niobium powder and aluminum powder, each havng a grain diameter between 1 and 400 microns, in proportions suitable to form an Al5 compound of the composition x% by weight Al and (100-x)% by weight Nb, wherein 5≦×≦20; (b) pressing said powder mixture into a tube formed of copper or a copper alloy having a greater hardness and higher mechanical tensile strength than copper, the interior of the tube having a diffusion barrier in the form of a coating of Ta or Ni of a thickness which is about 0.1 to 0.25 times the thickness of the tube, to form a filled tube; (c) cold forming the filled tube into wire comprising niobium filaments by swaging and drawing into wire, or by hydrostatic extrusion, swaging, and drawing into fine wire, wherein the cold forming takes place until the diameter D of the niobium filaments produced during cold forming is 0.1 microns ≦D≦1 micron; and (d) annealing the wire at a temperature between 923° and 1173° K. to form the Al5 phase.

Claim 2

A method for producing a superconductive wire of multifilaments having components comprising niobium and aluminum encased in copper or a copper alloy, wherein the multifilament configuration and the formation of a superconductive Al5 phase are positively developed from the components disposed in a copper or copper alloy tube having an interior metallic coating serving as a diffusion barrier, by cold forming and subsequent heat treatment, comprising the steps of: (a) mixing to form a powder mixture, niobium powder and aluminum powder, each havng a grain diameter between 1 and 400 microns, in proportions suitable to form an Al5 compound of the composition x% by weight Al and (100-x)% by weight Nb, wherein 5≦×≦20; (b) pressing said powder mixture into a tube formed of copper or a copper alloy having a greater hardness and higher mechanical tensile strength than copper, the interior of the tube having a diffusion barrier in the form of a coating of Ta or Ni of a thickness which is about 0.1 to 0.25 times the thickness of the tube, to form a filled tube; (c) cold forming the filled tube into wire comprising niobium filaments by swaging and drawing into wire, or by hydrostatic extrusion, swaging, and drawing into fine wire, wherein the cold forming takes place until the diameter D of the niobium filaments produced during cold forming is 0.1 microns ≦D≦1 micron; and (d) annealing the wire at a temperature between 923° and 1173° K. to form the Al5 phase.